What activation functions are currently popular?
Currently both ReLU and ELUs are the most popular activation functions (AF) used in neural nets (NNs). This is because they eliminate the vanishing gradient problem that causes major problems in the training process and degrades the accuracy and performance of NN models.
Also these AFs, more specifically ReLU, are very fast learning AF which make them even more useful in research.
However, depending on type of NN you working on, it's always a good practice to pay some attentions to new studies.